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Sex chromosome evolution in selected taxa of teleost fishes (Teleostei)
Pavlica, Tomáš ; Sember, Alexandr (advisor) ; Kratochvíl, Lukáš (referee)
Teleosts represent more than half of the extant vertebrate species. They show a wide range of mechanisms driving both sex determination and sex differentiation, including nine sex chromosome systems described to date. Teleost sex chromosomes are generally considered as evolutionarily young, therefore they are suitable for an analysis of the early stages of evolution of these unique genomic regions. The aim of the current thesis was to analyze the presence and degree of differentiation of sex chromosomes in two Nothobranchius killifish species and one Bunocephalus banjo catfish representative using conventional and molecular cytogenetic methods. Different populations of N. kadleci and N. furzeri analysed in this thesis shared anXY sex chromosome system. Despite the obvious heteromorphy of their sex chromosomes, comparative genome hybridization (CGH) did not show any region of differentiation. Analysis of synaptonemal complexes by immunostaining coupled with the mapping of 18S rDNA and telomeric repeats using fluorescent in situ hybridization (FISH) showed mainly standard pairing with the contribution of synaptic adjustment. Pachytene spreads of females from one N. furzeri population contained a small supernumerary chromosome which was not present in metaphases of studied somatic cells. Distribution...
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Evolution of sex chromosomes and karyotypes in geckos (Squamata: Gekkota)
Koubová, Martina ; Kratochvíl, Lukáš (advisor) ; Choleva, Lukáš (referee)
Gekkota is species-rich and diverse group of squamate reptiles (Reptilia: Squamata) with almost global distribution. There were many hypothesis defined about the phylogeny of this group, traditionally based on morphological data. The essential reversal in phylogenetic relationships occurred with the entry of molecular analysis, whose differ in their conclusions from traditional approach fundamentally, even in positions of mayor lineages. This fact has an essential importance for the karyotype evolution study of this group. The ancestral state is considered as 2n=38 karyotype with all chromosomes acrocentric. In some species is this karyotype kept, in another there is apparent an influence of chromosome changes, mostly Robertsonian fusions and pericentric inversions. Diploid chromosome number is from 16 to 46, but the most common is 2n=38 karyotype of mostly acrocentric chromosomes, gradually decreasing in size. The interesting character of this group is extraordinary variability in sex determining mechanisms. We can find there species with temperature sex determination and also species with genotypic sex determination (both types XX/XY and ZZ/ZW). Sex chromosomes data are documented in only 17 species. Sex chromosomes differ rapidly in their morphology and their homology between sister taxa was not proved...
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Molecular cztogenetic analysis of adaptive radiation in the gecko genus Paroedura (Squamata:Gekkota)
Koubová, Martina ; Kratochvíl, Lukáš (advisor) ; Šťáhlavský, František (referee)
Paroedura genus includes 17 described species endemic to Madagascar and the Comoros Islands, where they went through a significant adaptive radiation. The genus Paroedura is monophyletic and well supported hypothesis on phylogenetic relationships among its species was published. Species vary considerably in body size and morphology and in preferences for habitat, some species live in sympatry. The genus Paroedura belongs to cytogenetically poorly studied family Gekkonidae which exhibits high variability in modes of sex determination and in comparison with basal gecko lineages, also considerable variability in the chromosome number and morphology. Karyotypes of only two species of the genus (P. picta, P. sp.) have been published. The aim of my thesis was to describe karyotypes of both sexes in all available species of the genus using conventional and molecular cytogenetic methods, to perform the phylogenetic analysis of karyotype evolution and chromosomal rearrangements in the genus, to assess the role of these rearrangements in the speciation of the genus and to detect sex chromosomes. I acquired karyotypes of both sexes in nine species representing the most of major phylogenetic lineages of the genus. According to the results, species can be divided into three groups according to diploid...
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Karyotype analysis of selected groups of tetrapulmonate arachnids
Reyes Lerma, Azucena Claudia ; Sember, Alexandr (advisor) ; Johnson Pokorná, Martina (referee) ; de Bello Cioffi, Marcelo (referee)
Arachnids are a highly speciose group of arthropods with about 130 000 extant species from 12 orders. Some arachnid species are of economic and medical interest. They also offer various opportunities to study the link between genome and karyotype variability and morphological and ecological diversification, evolution and adaptation. The knowledge about arachnid karyotypes and genomes is, however, still limited. The available data show wide range of diploid chromosome numbers (2n), monocentric or holocentric chromosomal structure, variability in sex chromosome systems (especially in spiders) and modifications of meiosis. The main objective of this doctoral thesis was to study by conventional and molecular cytogenetic methods the mechanisms of karyotype evolution in haplogyne spiders (with monocentric and holocentric chromosomes), and further in two families (Charinidae and Phrynidae) from the closely related order Amblypygi. The selected groups offer unique insights into fundamental karyotype traits of the arachnid clade Tetrapulmonata, and they also enable to analyse the role of polyploidy in arachnid karyotype evolution and the evolutionary mechanisms behind the emergence of holocentric chromosomes. Our data suggest that holocentric chromosomes are an autoapomorphy for the haplogyne superfamily...
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Mechanisms of chromosome rearrangements and their relation to the formation of polyploid species
Vaňková, Tereza ; Knytl, Martin (advisor) ; Forman, Martin (referee)
Polyploid species are significantly represented among plants and some animals. Whole- genome duplication (WGD) is an unstable process with rapid changes in a genome and also changes in chromosomes. These changes includes chromosomal aberrations, such as translocations, duplications, insertion and inversions. Chromosomal aberrations and WGD are strongly represented in the evolution of organisms. Therefore the study of their mechanisms is important for an understanding of genomic development. At present, there are developments in cytogenetic technique helping study polypoid genomes and also helping add polyplodozation events to evolutionary contexts. These techniques includes banding as well as fluorescent in situ hybridization, which, thanks to the applicability of various probes, helps to detected chromosomal rearrangements. Keywords: Chromosome rearrangements, polyploid, WGD, cytogenetic techniques, FISH
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Mechanisms of chromosomal rearrangements in the context of polyploid species and its forming
Vaňková, Tereza ; Knytl, Martin (advisor) ; Forman, Martin (referee)
Polyploid species are significantly represented among plants and some animals. Whole- genome duplication (WGD) is an unstable process with rapid changes in a genome and also changes in chromosomes. These changes includes chromosomal aberrations, such as translocations, duplications, insertion and inversions. Chromosomal aberrations and WGD are strongly represented in the evolution of organisms. Therefore the study of their mechanisms is important for an understanding of genomic development. At present, there are developments in technique helping study polypoid genomes and also helping add polyplodozation events to evolutionary contexts. These techniques includes banding as well as fluorescent in situ hybridization, which, thanks to the applicability of various probes, helps to detected chromosomal rearrangements.
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Cytogenetics of selected groups of ray-finned fishes (Actinopterygii): Evolutionary-ecological questions associated with the dynamics of repetitive sequences and the occurrence of polyploidy
Sember, Alexandr ; Ráb, Petr (advisor) ; Marec, František (referee) ; Král, Jiří (referee)
Ray-finned fishes (Actinopterygii) exhibit the greatest biodiversity among vertebrates. The vast majority of extant actinopterygian fish species belong to clade Teleostei - a lineage whose significant evolutionary success might have resulted from a teleost specific whole- genome duplication (TSGD) that occurred at the onset of this group, subsequent to its divergence from the rest of actinopterygian lineages. Despite the growing body of sequenced fish genomes and analyses of their transcriptomes, the largest contribution to understanding fish genomes comes from analyses of DNA content and from cytogenetics. Genomes of ray-finned fishes and especially those of Teleostei exhibit vast diversity and rapid dynamics of repetitive DNA sequences whose variability is reflected in a wide range of fish genome sizes and in the dynamics behind karyotype differentiation. Therefore, ray-finned fishes offer a unique opportunity to study genome variability as a driving force underlying morphological and ecological diversification, evolution and adaptation. Particularly, the mapping of repetitive DNA sequences by means of fluorescence in situ hybridization (FISH) has proven to be a very useful and informative approach during the last two decades and contributed greatly to our understanding of the fish genome...
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Molecular cztogenetic analysis of adaptive radiation in the gecko genus Paroedura (Squamata:Gekkota)
Koubová, Martina ; Kratochvíl, Lukáš (advisor) ; Šťáhlavský, František (referee)
Paroedura genus includes 17 described species endemic to Madagascar and the Comoros Islands, where they went through a significant adaptive radiation. The genus Paroedura is monophyletic and well supported hypothesis on phylogenetic relationships among its species was published. Species vary considerably in body size and morphology and in preferences for habitat, some species live in sympatry. The genus Paroedura belongs to cytogenetically poorly studied family Gekkonidae which exhibits high variability in modes of sex determination and in comparison with basal gecko lineages, also considerable variability in the chromosome number and morphology. Karyotypes of only two species of the genus (P. picta, P. sp.) have been published. The aim of my thesis was to describe karyotypes of both sexes in all available species of the genus using conventional and molecular cytogenetic methods, to perform the phylogenetic analysis of karyotype evolution and chromosomal rearrangements in the genus, to assess the role of these rearrangements in the speciation of the genus and to detect sex chromosomes. I acquired karyotypes of both sexes in nine species representing the most of major phylogenetic lineages of the genus. According to the results, species can be divided into three groups according to diploid...
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Evolution of sex chromosomes and karyotypes in geckos (Squamata: Gekkota)
Koubová, Martina ; Kratochvíl, Lukáš (advisor) ; Choleva, Lukáš (referee)
Gekkota is species-rich and diverse group of squamate reptiles (Reptilia: Squamata) with almost global distribution. There were many hypothesis defined about the phylogeny of this group, traditionally based on morphological data. The essential reversal in phylogenetic relationships occurred with the entry of molecular analysis, whose differ in their conclusions from traditional approach fundamentally, even in positions of mayor lineages. This fact has an essential importance for the karyotype evolution study of this group. The ancestral state is considered as 2n=38 karyotype with all chromosomes acrocentric. In some species is this karyotype kept, in another there is apparent an influence of chromosome changes, mostly Robertsonian fusions and pericentric inversions. Diploid chromosome number is from 16 to 46, but the most common is 2n=38 karyotype of mostly acrocentric chromosomes, gradually decreasing in size. The interesting character of this group is extraordinary variability in sex determining mechanisms. We can find there species with temperature sex determination and also species with genotypic sex determination (both types XX/XY and ZZ/ZW). Sex chromosomes data are documented in only 17 species. Sex chromosomes differ rapidly in their morphology and their homology between sister taxa was not proved...
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